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Topic: Creation of larger sugars and dextrines from small sugars during mashing (Read 2738 times)

I just came across something that goes against what we have been told so far about starch conversion in mashing. It seems obvious that glucose chains are only split during mashing and that over time the length of the glucose chains goes down. Narziss and Back mention in Technologie der Würzebereitung that malt does contain transferase enzymes which can fuse glucose and maltose to form dextrins. Now the effect is not dramatic and doesn't really affect our simple model of mashing. But they mention it as one of the reasons why resting the main mash at 145 F for an extended time during a decoction does not affect the fermentability significantly. The other reason is the already diminished b-amylase activity.

I thought that wa interesting. I'll have to see if I can find a reference in English.

Drunk though I may be, I'm curious. How does this mesh with the supposed Miller/Coors mash temps in the 145 range to create a highly fermentable wort? Is the idea that the "extended times" of the decoction rest do not approach the time necessary to break down the chains?

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In past batches where I compared a Hochkurz decoction to an equivalent infusion mash I always pulled the decoction after a shorter rest than I was using for the infusion version. My recent Maibock was brewed like this where the infusion version had a 45 min rest at 145 and the decoction version pulled the deciction after 30 min of resting at 45 min. Both batches ended up with about 80% attenuation limit. The decocted version had a slightly higher attenuation limit (maybe by 1%).

I think that there are many factors at play here that make it difficult to state that the rest at 145 F during the decoction processing doesn’t affect fermentability. But it is not such that one has to worry about it that much. Even if it takes a long time it will not dry out your beer. There are also plenty of dextrines that are formed from the starches and long dextrines in the decoction once it is added back to the main mash.

The interesting take-away here was the existence of enzymes that put sugars back together to form dextrines. If you think about it, those enzymes have to exist in the kernel while it is growing since that is how starch is formed. And it is just logical that some of them survive into malt although these are not the enzymes that are formed during germination and their effect on mashing is more of a theoretical and geeky nature than a real practical one.

I forgot to mention this. But the existence and activity of these enzymes was also mentioned as one factor why thick mashes don’t necessarily give higher fermentable worts even though the b-amylase is more stable in thick mashes. The latter should cause longer b-amylase activity. But the high sugar concentration causes inhibitory effects and also leads to the re-formation of dextrines through aforementioned enzymes.

So to carry this over into practical brewing where say a brewer wantedto produce more food (complex sugars) for a Brettanomyces strain that was to ferment after a Saccromyces ferment, a brewer should.....uh...uh.....mash at...uh...

The interesting take-away here was the existence of enzymes that put sugars back together to form dextrines. If you think about it, those enzymes have to exist in the kernel while it is growing since that is how starch is formed. And it is just logical that some of them survive into malt although these are not the enzymes that are formed during germination and their effect on mashing is more of a theoretical and geeky nature than a real practical one.

Very interesting, indeed! Now we have to figure out how that relates to our processes and results.

Very interesting, indeed! Now we have to figure out how that relates to our processes and results.

That’s all it really is: “very interesting”. It complicates our simple view of how sugars are created but the net effect is simply that the resulting simple sugars are a bit less than what you would expect by just looking at b-amylase activity. To compensate for that you may just assume that the b-amylase appears to be a bit less active than assumed. That’s how I would handle this in the simple model we have about mashing. The main thing to take away from here is that things are more complicated that we assume which makes it difficult to model mashing and use that to predict fermentability. In the end you have to use your experience from past batches to guide your mash parameters which is something that others and I have been saying all along.

What would be really interesting would be some data on the reaction rates at various temperatures and mash ratios. I wonder if there's a point at which the transferase reaction would actually be favored over the amylases? I searched a couple of journal databases but didn't really turn up anything relevant.

I guess from a practical perspective the effects are going to be known (if only intuitively) by the second or third time you conduct a particular mash. "This attenuated a little too much - let's just mash one degree higher next time." So maybe no one's ever seen a need to do the research. Or maybe the effect is so minor there simply isn't one.

So to carry this over into practical brewing where say a brewer wantedto produce more food (complex sugars) for a Brettanomyces strain that was to ferment after a Saccromyces ferment, a brewer should.....uh...uh.....mash at...uh...

___________ _________ _________ (fill blanks please)

Don't over think this. Just mash at a higher temp. Don't try to create dextrines via this mechanism. Just don't make as much simple sugar. This is easier to control.

I think that there are many factors at play here that make it difficult to state that the rest at 145 F during the decoction processing doesn’t affect fermentability. But it is not such that one has to worry about it that much.

I think that this is the key to understanding. Assuming that the research is true, that these enzymes exist in the mash and that they are capable of forming complex sugars and dextrins from simple sugars, the question becomes, "Under what conditions will these enzymes form said compounds?" That they are present and able to do so under some conditions is a long way from surmising that they do so under the specific conditions that concern us.

I brought up the extended (1.5-2hr) low temperature (145f) mash schedule because I have heard tell that this is how some of the American lager producers are able to produce such a high level of attenuation. If we assume that is true, and assume that they, having a great deal of experimental knowledge on the subject, would not go through such an expense if it were not necessary, it seems to me that either the extended time is required for the amylase to break down the sugars that have just been formed by the transferase OR neither the transferase is able to recombine sugars under the extended mash conditions, nor are the amylase able to break down the starch significantly during the abbreviated (45m) rest at that temperature. Or some combination thereof.

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“If one's actions are honest, one does not need the predated confidence of others, only their rational perception.”

It lists the attenuation limit (fermentability) for 2 sets of mashes done at different mash thicknesses.

The first set used the congress mash where you have a 1 C/min rise from 45 C to 70 C. At 70 C the mash is rested until fully converted. This is not a practical mash for brewing. It is a laboratory mash used for evaluating malt.

The 2nd set of experiments used the same mash profile with the exception of an added 30 min rest at 64 C. The experiments were done for mash thicknesses ranging from 2 l/kg to 5 l/kg (~1 – 2.5 qt/lb).

As you can see the addition of the 64 C (~147 F) rest was able to boost the attenuation limit in all cases, except for the very thick mash. The explanation given was that the thicker mashes are able to better protect the b-amylase with resulted in more fermentable wort for thick mashes in the 1st experiment.

A 30 min rest at 64 C was able to compensate for that and because of the aforementioned formation of dextrines from sugars, which seems to be greatly accelerated in thick mashes, the fermentability actually drops for the 2 l/kg mash when a rest at 64 C is added. It seems that these enzymes are most effective in thick mashes. This reminds me of the discussion whe had a while back when I found conflicting statements about how mash thickness affects fermentability. This data shines a little bit more light onto the subject and while it is not able to simplify the matter it can exlplain why the data on that seems so conflicting.

When I evaluated the effect of mash thickness on attenuation I used isothermal mashing (fancy word for single infusion) , which is different from these experiments, and was not able to detect a significant effect on attenuation. The same is true for the series with the 64 C rest which where you see a difference of 2% between the best and the worst.

BTW, the last row in the table shows the time in min that it took for the mash to fully convert once the 70 C rest was reached. It confirms my statements that tinner mashes tend to convert faster which can show itself as a boost in efficiency.

It should have been, I'm just dense and wanted to make sure I was referencing the table correctly. Thanks.

Edit: So just to be certain I'm reading this correctly, the numbers in the top row are for the congressmash alone (baseline), the next row is a congress mash with an additional 30 min. rest @64c, and the bottom row relates to that row showing the time it took the mash to convert under those conditions. Correct?

« Last Edit: March 26, 2010, 12:12:14 PM by MrNate »

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“If one's actions are honest, one does not need the predated confidence of others, only their rational perception.”